How to tell what rear end is in a Chevy truck?

In most Chevy trucks, the rear axle (rear end) can be identified by reading axle tags or stamps, inspecting the differential, and cross-referencing the vehicle’s documentation. The quickest way is to locate any metal tags on the axle or housing and decode them, then confirm with the VIN/build sheet or owner’s manual.

Where to look on the truck

Start by inspecting the rear axle assembly itself. Look for a tag attached to the differential cover or axle tube; it often carries a code or ratio. If there’s no tag, examine stamping on the differential housing or cover edge for markings. In many GM trucks, the original build sheet or a glove box/door jamb sticker can also list the axle ratio or axle option codes.

Before listing the steps, here’s what you’ll typically do to identify the rear end.



• Locate and read any axle code tag on the differential cover or nearby axle tube; the code indicates the axle family and gear ratio.


• Open the differential cover carefully to check for stamped markings, the carrier type, and any ratio figures stamped into the ring gear or carrier housing.


• Observe physical traits such as the number of bolts on the differential cover and whether the axle is full-floating or semi-floating, as these are common distinguishing features.


• Check the vehicle’s VIN, build sheet, or glove box sticker for axle-related RPO (Regular Production Option) codes that specify the original rear end configuration.

Concluding paragraph: By combining tag/stamp information with physical characteristics and the vehicle’s paperwork, you can reliably determine which rear end is in your Chevy truck and its gear ratio.

How to decode common GM axle information

To identify the exact rear axle type and gear ratio, you’ll typically decode codes from tags or stamping and cross-check with GM’s documentation. The process works across generations, though specific codes vary by year and model. If you’re unsure, reference guides and forums specific to Chevy trucks can be very helpful.

1. Read the axle code or ratio shown on the tag or stamped on the differential housing; this code points to the axle family and gear ratio.


2. Look for option codes such as locking differential indicators (for example, a code like G80 on GM trucks indicates an automatic locker) and cross-check with factory RPO documentation.


3. Note the axle’s mechanical design (full-floating vs semi-floating) as well as the carrier style; these details narrow the possibilities for the rear end type.


4. Match the observed features to a GM axle chart or owner-supplied documentation for the model year; many GM trucks used distinct rear-axle families in different eras (for example, common families include lighter-duty and heavy-duty configurations).


5. If available, verify with a de-coded VIN/build sheet or with a dealership/service manual; these sources often list the original rear axle specification for a given VIN.

Concluding paragraph: Decoding the codes and verifying with official references will give you a precise identification of the rear end, including the axle family, gear ratio, and whether a factory locker was installed.

Tips and cautions for accuracy

- Photos help: Take clear pictures of any axle tag, stamping, and the differential cover area to share with a knowledgeable forum or technician.

– Safety first: When removing the diff cover or handling fluid, use proper tools and dispose of old gear oil responsibly.

– Documentation matters: If you have the vehicle’s build sheet or a glove box sticker, it’s often the fastest route to an accurate diagnosis.

Summary

To determine which rear end is in a Chevy truck, start with physical cues like tags, stamps, the number of differential-cover bolts, and the presence of full-floating versus semi-floating designs. Read axle codes from tags or stamping, check the gear ratio markings, and cross-check with the vehicle’s VIN/build sheet or RPO documentation. If the markings are unclear, consult GM axle charts, relevant forums, or a qualified shop to confirm the exact rear-axle family and gear ratio.

How do I know if I have a 3.73 or 4.10 gear?

And since we live in the day and age of 2025. Uh if you're curious. You can easily. Google you know uh the number of teeth on a ring gear.

Does the VIN number tell you the gear ratio?

You may be able to tell the gear ratio from a vehicle's VIN by using an online VIN decoder, though not all manufacturers include this information in the VIN itself. If the gear ratio is included, it will likely be in the Vehicle Descriptor Section (VDS), which are the 4th through 8th digits of the VIN. For many vehicles, a sticker on the driver's side door jamb or on the vehicle's build sheet or owner's manual is a more reliable way to find the gear ratio. 
How to check the VIN

• Use an online VIN decoder: Enter the full VIN into a free online decoder. Some manufacturers have their own decoders, such as Mopar's decoder. 
• Look for the gear ratio code: Some VINs will have a code within the VDS that represents the gear ratio (e.g., "3731"). 
• Consult the manufacturer: If the VIN decoder doesn't provide the information, contact the vehicle manufacturer for assistance. 

Other methods to find the gear ratio

• Check the vehicle sticker: Look for a sticker on the driver's side door jamb or on the vehicle's build sheet. This sticker often contains detailed information about the vehicle's equipment, including the axle ratio. 
• Look at the differential: Some differentials have a metal tag with the gear ratio stamped on them, or there may be a sticker on the axle itself. 
• Consult your owner's manual: The owner's manual or other paperwork from the vehicle's purchase often lists the gear ratio. 

How do I know what rear end I have in my Chevy truck?

You can identify your Chevy truck's rear end by checking the "Service Parts Identification" sticker, which contains RPO codes, or by manually inspecting the differential cover for markings and measuring it. The sticker in your glove box or door jamb is the easiest way to find the original rear end type and ratio without any modifications. If the sticker isn't there or the rear end was changed, you'll need to inspect the differential cover or count gear teeth, notes JustAnswer, West Coast Differentials, Chevy Hardcore, and Facebook.
 
Method 1: Check the RPO codes

1. Locate the sticker: Look for a sticker labeled "Service Parts Identification" inside the driver's door jamb, glove box, or owner's manual. 
2. Find the axle code: Look for a two-letter code starting with "G," which represents the axle. Examples include "G80" for a locking differential or "GU5" for a 3.23 gear ratio. 
3. Decipher the code: You can find a list of GM RPO codes online to identify the specific model and gear ratio. 

Method 2: Inspect the differential cover 

1. Look for tags or stamps: The differential cover may have a tag with the model number or other identifying information. 
2. Check the shape and size: The size and shape of the cover can help narrow down the options. For example, the 8.5-inch 10-bolt has a larger, oval-shaped cover than the 7.5-inch 10-bolt, which has an oval cover measuring approximately 8 5/16 inches by 10 9/16 inches. 
3. Measure for confirmation: If the cover is difficult to read, you can measure it. The 7.5-inch 10-bolt cover, for instance, has a specific bolt spacing on the bottom, notes Chevy Hardcore. 
4. Look for a 14-bolt: If you have a heavy-duty truck, you might have a 14-bolt axle, which has a distinct, more complex-looking cover than the 10-bolt. 

Method 3: Count the gear teeth (if you're comfortable with this)

1. Safely raise the vehicle: Jack up the truck and secure it with jack stands. 
2. Drain the differential fluid: Remove the differential cover and drain the old fluid. 
3. Count the teeth: Count the teeth on the ring gear (the larger gear) and the pinion gear (the smaller gear). 
4. Divide to find the ratio: Divide the number of teeth on the ring gear by the number of teeth on the pinion gear to find your gear ratio. 
   • For example, a ring gear with 41 teeth and a pinion gear with 11 teeth would give you a ratio of 41÷11≈3.7341 divided by 11 is approximately equal to 3.7341÷11≈3.73. 
   • If the gear is labeled with the ratio directly (e.g., "41:11"), you can use that. 

Important note

• Modifications: Be aware that some of these methods, especially RPO codes, will only be accurate if the rear end has not been changed or modified. 
• Professional help: If you're not comfortable with these steps, take the truck to a mechanic for a professional assessment. 

How do I figure out what rear differential I have?

You can identify your rear differential by checking for a factory-installed ID tag on the differential cover or axle tube, or by using visual characteristics like the number of bolts on the cover, the shape of the cover, the diameter of the ring gear, and whether it is an integral or dropout design. If all else fails, you can use your vehicle's VIN or the axle code on the driver's side door jamb, and a mechanical inspection of the axle's behavior when a wheel is spun can help determine if it's an open or limited-slip differential. 
Method 1: Check for tags and codes

• Vehicle information sticker: Look for a sticker in the driver's side door jamb or on the vehicle's door for an axle code. You can look up this code online to find the factory specifications, notes the Ford support page. 
• Differential cover tag: Look for a small metal tag bolted to the differential cover, usually under one of the bolts. It may have a gear ratio code stamped on it, like "410" for 4.10 gears, and sometimes a "L" for a limited-slip differential, explains this YouTube video. 
• Axle tube stamp: Some vehicles have a stamp directly on the axle housing itself, notes BigMackTrucks.com. 

Method 2: Visual and physical inspection

• Number of cover bolts: Most differentials can be identified by the number of bolts on the differential cover, commonly 10, 12, or 14 bolts. 
• Cover and housing shape: Note the shape of the cover and whether the differential has an integrated housing or a dropout style where the entire assembly is removed from the front. 
• Ring gear size: Once the cover is removed, you can measure the diameter of the ring gear from tooth tip to tooth tip. 
• Axle shaft and spline count: You can count the number of splines (the raised teeth) at the end of the axle shaft. You can also measure the shaft length, which differs for semi-float vs. full-float axles, notes this YouTube video. 

Method 3: Test the differential type 

• Open differential: Jack up the rear of the vehicle so both rear wheels are off the ground. Put the transmission in neutral and spin one rear wheel. If the opposite wheel spins in the opposite direction, it's an open differential.
• Limited-slip or posi-traction: If both wheels spin in the same direction, it is a limited-slip (or "posi") differential. 

Method 4: If all else fails

• Consult the dealer or a workshop: The Ford support page suggests contacting the dealer or visiting a professional workshop. 
• Owner's manual: The owner's manual may list the axle specifications or code.